Aim. Shoulder prosthesis chronic infection is a rare but serious complication, likely to lead to re-interventions and poor functional outcome. Two-stage exchange surgery is considered the standard procedure by most authors. Our hypothesis was that one-stage revision procedure is a valid therapeutic option in the management of chronic infections of shoulder arthroplasty. Method. This was a mono-center retrospective cohort study. All patients who underwent, during the inclusion period, a one-stage revision procedure for a chronic infection of shoulder arthroplasty were included. All patients underwent clinical evaluation (Constant-Murray score), radiological examination (standard X-rays) and a blood test (Complete Blood Count and C-reactive protein), at a minimal one-year follow-up. Primary endpoint of this study was the infectious outcome and secondary endpoints were the functional and radiographic outcomes. Results. 16 shoulder prosthesis in 14 patients (5 females, 9 males) were included. Mean time between primary prosthesis implantation and exchange surgery was 40 months (1–145). Mean follow up was 30,5 months. The principal micro-organism involved was Propionibacterium acnes (9/16) and multiple organisms were found in 6 patients. In 14/16 (87,5%) shoulders, we found no sign of persistent infection at last follow-up. 2/16 (12,5%) shoulders were considered as still infected. On these 2 patients still infected, one refused further revision and the other was not in a good enough medical condition to undergo another procedure. 2 patients required an additional one-stage procedure for a new infection (new pathogen) after a period of two years, both free of infection at last follow-up. At last follow-up, mean Constant score was 54,8 (23–82). 7/14 (50%) patients were satisfied or very satisfied with the global fonctionnal result. Conclusions. One-stage revision procedure seems to be a valid therapeutic option in the management of infected shoulder prosthesis, as it allowed us to eradicate the infection in 87,5% patients in our serie, with a fair clinical result

Aim. A significant number of patients undergoing shoulder arthroplasty surgery have C acnes contamination at the end of the primary surgery. The objective of this study is to determine whether patients with C acnes contamination at the end of their primary shoulder surgery have a worse prognosis than those who end up without C. acnes contamination. Method. Prospective study including all patients who underwent a reverse shoulder prosthesis from January 2015 to December 2018. In all of them, 5 to 12 cultures were performed during primary surgery. The patients underwent surgery for shoulder arthritis secondary to rotator cuff tears, acute fracture of the proximal humerus, and sequelae of fracture of the proximal humerus. Exclusion criteria included the existence of previous surgeries on the affected shoulder, the presence of signs of infection, having received infiltrations and / or complementary invasive examinations (Arthro-MRI and Arthro-CT). Follow-up from 2 to 5 years. Functional assessment according to the Constant Functional Scale. All complications were also recorded. Results. 162 patients were included. Of these, 25 had positive cultures for C. acnes at the end of primary shoulder surgery. Average age of 74.8 years. 136 women and 26 men. 75.9% Shoulder arthritis secondary to rotator cuff tears, 13.6% acute fractures and 10.5% sequelae of fractures. There were no differences between patients with C. acnes and those without C. acnes regarding age and indication for surgery. Predominance of men in the group with positive C. acnes (p <0.001). No differences at 2 and 5 years in the Constant functional scale between the two groups (2 years, 59.6 vs 59.2 p 0.870) (5 years, 62.4 vs 59.5 p 0.360). Significant differences regarding the number of complications (p 0.001). Patients without C. acnes had 1 aseptic loosening of the metaglene and patients with C. acnes had 2 infections, 1 dislocation, and 1 revision surgery. Patients with contamination by C. acnes had more comorbidities (p 0.035) than patients without contamination. Conclusions. Patients with C acnes contamination at the end of primary surgery do not have functional differences when compared with patients without contamination at 2 and 5 years, but they have a higher number of complications in the medium term

Introduction. Modern prostheses of the 3rd and 4th generation facilitate a precise adjustment to various humeral anatomies. This provides major advantages regarding soft tissue balancing and the reconstruction of the rotational center. Thus, high expectations are linked to the use of modern shoulder prostheses compared to conventional designs. Methods. Out of a prospective multicenter study, 108 cases (72 females, 36 males) were reviewed. All patients were treated with the same type of double eccentric shoulder prosthesis. The mean age at surgery was 71.5 years (range, 44.6 to 97.3). The Constant Score (CS), ASES Score, X-rays and complications were evaluated at 3, 6, 12 and 24 months as well as 4, 7 and 10 years follow-up. Results. At a mean follow-up time of 93.3 months, the mean CS improved from preoperative 25.6 (±8.8) to 63.8 (±19.1) points at 7 years. In the same period, the mean ASES Score improved from 24.5 (±12.5) to 79.6 (±19.1). Pain according to the CS was rated preoperatively as high (mean 1.8 points). After 7 years patients suffered from mild to no pain (mean 12.0 points). A total of 7 prostheses were revised, leading to an overall survival rate of 91.5% at 10 years. In 4 cases secondary glenoid erosion was the reason for revision. Conclusion. The clinical results of the investigated prosthesis system are convincing and comparable to other modern shaft prostheses. To achieve an anatomical reconstruction of the rotational center of the humeral head, the use of a double eccentric shoulder prosthesis is recommended

Purpose. Reverse shoulder prosthesis may lead to scapular notching, caused by attrition of the upper humeral component with scapular neck. We compared the clinical and radiographic results obtained with a SMR prosthesis, which allows a concentric or an eccentric glenosphere to be applied. Patients and methods. 67 patients, mean age 73 years, were treated with reverse prosthesis using concentric and eccentric glenosphere. In patients with concentric glenosphere, the glenosphere extended about 4 mm below the glenoid. The eccentric glenosphere protected the upper glenoid neck by its inferior prolongment. Patients were followed for a mean of 33 months. At final F-U the Constant Score (C.S.) and the score with the Simple Shoulder test (S.S.T.) were calculated. Radiographs were obtained to evaluate the presence of scapular notching, psna (prosthesis-scapular neck angle), pgrd (peg- glenoid rim distance) and DBSNG (distance between scapular neck and glenosfere). Included in this study were patients, as much homogeneous as possible by age and pathology, 25 with concentric (Group I) and 30 with eccentric (Group II) glenosphere, who had a minimum F-U of 24 months. Statistical analysis was performed with a paired test. Results. 25 patients of group I and 26 in group II were available for the study. In Group I mean elevation improved from 78° to 122° and mean abduction from 71° to 98°; in Group II from 66° to 148° and 60° to 115°. External and internal rotations were similar in both groups. 14 (56%) patients of Group I, and none of Group II had scapular notching (p<0.001). CS increased from 38 pt to 69 pt in Group I and from 30 pt to 74 pt in Group II. Conclusions. Low implantation of glenosphere did not eliminate scapular notching. Instead, no notching was detected with eccentric glenosphere, which also increased the ROM. The PSNA, DBSNG, PGRD are reliable measures to predict scapular notching

Background. One of the main concern about reverse shoulder arthoplasty for the treatment of rotator cuff deficiency is scapular notching that is still an unsolved issue for this particular prosthesis. The purpose of this multicentric retrospective study is to compare two different concept of reverse prosthesis, one with a concentric glenoshere and the other one with a new eccentric glenoshere design that aim to minimize scapular notching. Methods. From 2004 to 2009 67 patients were treated with a SMR reverse shoulder prosthesis (LIMA) with either concentric (figure 2) or eccentric glenosphere (figure 1). We selected for the study patients with criteria as much homogeneous as possible by the age and pathology. We then included for the study 25 patients (Group 1) with a concentric glenosphere and 21 (Group 2) with a eccentric glenosphere. All baseplates of concentric glenospheres were implanted with the most inferior aspect of baseplate that matched with the inferior glenoid ream, so that the glenosphere extended 4 mm beyond the glenoid inferiorly in order to minimize scapular notching. Every patient were followed clinically (Constant and Murley Score [C.S.] and Simple Shuolder test [S.S.T.]) and radiographically (notching, loosening and mechanical failure) with a minimum follow-up of 24 months. We also evaluated at the final follow-up psna (prosthesis-scapular neck angle), pgrd (peg glenoid rim distance) and DBSNG (distance between scapular neck and glenosfere). Results. At two years of follow up R.O.M. increased significantly in both groups especially in those with a eccentric glenosphere. Notably in patients with an eccentric glenosphere elevation improved from 66° to 148° and abduction from 60° to 115° while in those with a concentric glenosphere improved from 78° to 122° and 71° to 98° respectively for elevation and abduction. Outcomes for external-rotation and internal-rotation were very similar in both groups. 14 (56%) patients among those with a concentric glenosphere had scapular notching while we didn't have any notch in those with eccentric glenosphere even though we didn't find any significant different between the two groups in term of clinical outcomes and patient's satisfaction. The average C.S. increased from 38% to 69% in those with concentric SMR and from 30% to 74% in the other group. At the final follow-up PSNA, DBSNG and PGRD were respectively 88°, 3,2mm and 18,2 mm in group 1, while they were 92°, 4,3 mm and 21,2 mm in the group 2. Conclusions. Putting concentric glenosphere more inferiorly reduce the incidence of scapular notching but it doesn't solve the problem whereas, at medium follow-up, the new eccentric design seems to solved completely this issue. This study sustains PSNA, DBSNG, PGRD as reliable measures to predict scapular notching. Besides eccentric SMR glenosphere seems to increase R.O.M. mostly in flexion, abduction and adduction

Introduction

Loosening of the baseplate is one of the most common causes of failure in Reverse Shoulder Arthroplasty. To allow osteo-integration to occur and thus provide long-term stability, initial screws fixation plays a pivotal role. In particular, tightening torque and force of nonlocking screws are two parameters that are considered to have a clear impact on implant stability, yet the relation is not fully understood. For this reason, this study aims to define an experimental set-up, to measure force and torque in artificial bone samples of different quality, in order to estimate ranges of optimal surgical values and give guidelines to maximize screw fixation and therefore initial implant stability.

Background

Stemless prostheses are recognized to be an effective solution for anatomic total shoulder arthroplasty (TSA) while providing bone preservation and shortest operating time. Reverse shoulder arthroplasty (RSA) with stemless has not showed the same effectiveness, as clinical and biomechanical performances strongly depend on the design. The main concern is related to stability and bone response due to the changed biomechanical conditions; few studies have analyzed these effects in anatomic designs through Finite Element Analysis (FEA), however there is currently no study analyzing the reverse configuration. Additionally, most of the studies do not consider the effect of changing the neck-shaft angle (NSA) resection of the humerus nor the proper assignment of spatial bone properties to the bone models used in the simulations. The aim of this FEA study is to analyze bone response and primary stability of the SMR Stemless prosthesis in reverse with two different NSA cuts and two different reverse angled liners, in bone models with properties assigned using a quantitative computed tomography (QCT) methodology.

Background

Locked anterior shoulders (LAS) with static instability and anterior glenoid bone loss are challenging in the elderly population. Reverse shoulder arthroplasty (RSA) has been employed in treating these patients. No study has compared RSA for LAS to classically indicated RSA.

Introduction

Reverse total shoulder arthroplasty continues to have a high complication rate, specifically with component instability and scapular notching. Therefore, the purpose of this study was to quantify the effects of humeral component neck angle and version on impingement free range of motion.

Background

When reversing the hard-soft articulation in inverse shoulder replacement, i.e. hard inlay and soft glenosphere (cf. Figure 1), the tribological behaviour of such a pairing has to be tested thoroughly. Therefore, two hard materials for the inlay, CoCr alloy and alumina toughened zirconia ceramic (ceramys®) articulating on two soft materials, conventional UHMWPE and vitamin E stabilised, highly cross-linked PE (vitamys®) were tested in a joint simulator.

Introduction:

90 cases of reversed prosthesis have been evaluated and the aim of the retrospective multicenter study was to correlate the functional and radiological results depending on the type of implant.

Introduction. Shoulder arthoplasty has increased in the last years and its main goal is to relieve pain and restore function. Shoulder prosthesis enters in the market without any type of pre-clinical tests. Within this paper we present study experimental and computational tests as pre-clinical testing to evaluate total shoulder arthoplasty performance. Materials and methods. An in vitro experimental simulator was designed to characterize experimentally the intact and implanted shoulder glenoid articulation. Fourth generation Sawbones® composite left humerus and scapula were used and the cartilage was replicated with silicone for the intact articulation (figure 1). In the intact experimental articulation we considered the inferior glenohumeral ligament as an elastic band with equivalent mechanical properties. For the implanted shoulder, the Comprehensive® Total Shoulder System (Biomet®) with a modular Hybrid® glenoid base and Regenerex® central post was considered (figure 2). The prostheses were implanted by an experienced surgeon and clinical results from orthopedic registers were collected. The system structures were placed to simulate 90º in abduction, including the following muscle forces: Deltoideus 300N, Infraspinatus 120N, Supraspinatus 90N and Subscapularis 225N. The finite element model was created with tetrahedral linear elements with linear elastic and isotropic material for the humerus in figure 3, (Young's modulus for cortical bone − 16.5 GPa; trabecular bone − 124 MPa). Anisotropic behavior was considered for the scapula model (E11 = 342.1 MPa, E22 = 212.8 MPa, E33 = 194.4 MPa). The shoulder prosthesis was of polyethylene with 1GPa and titanium with 110 GPa. The Poisson's ratio was 0.3 in all material, except for polyethylene where we assumed a value of 0.4. A long-term post-operative condition was simulated. Results. The experimental results were compared with numerical ones for model validation. The strains measured evidence the effect of the implant presence, manly in the scapula. In the anterior region presents an increase of strains (+26%) was observed for the anterior region and decrease (−52%) in the posterior region, suggesting strain shielding in figure 4. At the glenoid cavity, the numerical principal strains present safety values of strains (200 to 2500) µε in both axial and coronal planes. This indicates that on the long-term the glenoid prosthesis is well fixed to the surrounding bone tissue and bone integrity is maintained despite the presence of the implant. However there are some peak values (2500, 25 000 µε) that were observed in some small areas in the posterior and distal regions. Results were compared with clinical ones. Discussion and Conclusions. The proposed pre-clinical test with the articulation at 90º in abduction can predict bone behavior when total shoulder prosthesis is implanted and in the long term post-operative condition. The results obtained evidence some critical regions around the glenoid component. This pre-clinical test can be implemented to improve the concepts before market

Introduction. Machine learning is a relatively novel method to orthopaedics which can be used to evaluate complex associations and patterns in outcomes and healthcare data. The purpose of this study is to utilize 3 different supervised machine learning algorithms to evaluate outcomes from a multi-center international database of a single shoulder prosthesis to evaluate the accuracy of each model to predict post-operative outcomes of both aTSA and rTSA. Methods. Data from a multi-center international database consisting of 6485 patients who received primary total shoulder arthroplasty using a single shoulder prosthesis (Equinoxe, Exactech, Inc) were analyzed from 19,796 patient visits in this study. Specifically, demographic, comorbidity, implant type and implant size, surgical technique, pre-operative PROMs and ROM measures, post-operative PROMs and ROM measures, pre-operative and post-operative radiographic data, and also adverse event and complication data were obtained for 2367 primary aTSA patients from 8042 visits at an average follow-up of 22 months and 4118 primary rTSA from 11,754 visits at an average follow-up of 16 months were analyzed to create a predictive model using 3 different supervised machine learning techniques: 1) linear regression, 2) random forest, and 3) XGBoost. Each of these 3 different machine learning techniques evaluated the pre-operative parameters and created a predictive model which targeted the post-operative composite score, which was a 100 point score consisting of 50% post-operative composite outcome score (calculated from 33.3% ASES + 33.3% UCLA + 33.3% Constant) and 50% post-operative composite ROM score (calculated from S curves weighted by 70% active forward flexion + 15% internal rotation score + 15% active external rotation). 3 additional predictive models were created to control for the time required for patient improvement after surgery, to do this, each primary aTSA and primary rTSA cohort was subdivided to only include patient data follow-up visits >20 months after surgery, this yielded 1317 primary aTSA patients from 2962 visits at an average follow-up of 50 months and 1593 primary rTSA from 3144 visits at an average follow-up of 42 months. Each of these 6 predictive models were trained using a random selection of 80% of each cohort, then each model predicted the outcomes of the remaining 20% of the data based upon the demographic, comorbidity, implant type and implant size, surgical technique, pre-operative PROMs and ROM measures inputs of each 20% cohort. The error of all 6 predictive models was calculated from the root mean square error (RMSE) between the actual and predicted post-op composite score. The accuracy of each model was determined by subtracting the percent difference of each RMSE value from the average composite score associated with each cohort. Results. For all patient visits, the XGBoost decision tree algorithm was the most accurate model for both aTSA & rTSA patients, with an accuracy of ∼89.5% for both aTSA and rTSA. However for patients with 20+ month visits only, the random forest decision tree algorithm was the most accurate model for both aTSA & rTSA patients, with an accuracy of ∼89.5% for both aTSA and rTSA. The linear regression model was the least accurate predictive model for each of the cohorts analyzed. However, it should be noted that all 3 machine learning models provided accuracy of ∼85% or better and a RMSE <12. (Table 1) Figures 1 and 2 depict the typical spread and RMSE of the actual vs. predicted total composite score associated with the 3 models for aTSA (Figure 1) and rTSA (Figure 2). Discussion. The results of this study demonstrate that multiple different machine learning algorithms can be utilized to create models that predict outcomes with higher accuracy for both aTSA and rTSA, for numerous timepoints after surgery. Future research should test this model on different datasets and using different machine learning methods in order to reduce over- and under-fitting model errors. For any figures or tables, please contact the authors directly

Purpose. Total shoulder arthroplasty (TSA) has become a successful treatment option for degenerative shoulder disease. With the increasing incidence in primary TSA procedures during the last decades, strategies to improve implant longevity become more relevant. Implant failure is mainly associated with mechanical or biological causes. Chronic inflammation as a response to wear particle exposure is regarded as a main biological mechanism leading to implant failure. Metal ions released by fretting and corrosion at modular taper connections of orthopedic implants can cause cell-mediated hypersensitivity reactions and might lead to aseptic loosening. Modularity is also commonly used in total shoulder replacement. However, little is known about metal ion exposure in patients following TSA. The objective of this study was to determine in-vivo blood metal ion levels in patients after TSA and to compare blood metal ion levels to control subjects without metal implants. Methods. A total of 19 patients with anatomical total shoulder prosthesis (TSA group) and 20 patients with reverse total shoulder prosthesis (RSA group) who underwent unilateral total shoulder replacement at our hospital between March 2011 and December 2014 with no other metal implant or history of environmental metal ion exposure were recruited for analysis of blood metal ion concentrations of cobalt (Co), chromium (Cr) and titanium (Ti) at a mean follow-up period of 2.3 years (0.7–4.3). For comparison of metal ion concentrations blood samples were obtained in a healthy control group of 23 subjects without metal implants. Ethical approval and informed consent of each patient were obtained for this study. Results. Median cobalt ion levels were 0.14µg/l (range 0.03–0.48) in the TSA group, 0.18 µg/l (0.10–0.66) in the RSA group and 0.11µg/l (0.03–0.19) in the control goup. Median chromium ion levels were 0.34µg/l (0.09–1.26) in the TSA group, 0.48µg/l (0.17–2.41) in the RSA group and 0.14µg/l (0.04–0.99) in the control goup. Median titanium ion levels were 0.86µg/l (0.10–1.64) in the TSA group, 1.31µg/l (0.75–4.52) in the RSA group and 0.62µg/l (0.32–2.14) in the control goup. There was a statistically significant difference in chromium and titanium ion concentrations between both study groups and the control group (see figure 1–3). Conclusion. Patients with unilateral total shoulder replacement demonstrated elevated blood metal ion concentrations. Median blood metal ion levels were higher in the RSA group compared to the TSA group, which could be attributable to the modularity of the reverse total shoulder system. However, overall metal ion levels were relatively low compared to those seen in patients with metal-on-metal total hip replacements. The role of local metal ion exposure in the development of aseptic loosening or hypersensitivity reactions associated with total shoulder arthroplasty should be further investigated. For figures/tables, please contact authors directly.

Aim. Cutibacterium acnes (CA) is one of the crucial actors in spine instrumentation or shoulder prosthesis. Its population is subdivided into 6 major phylotypes: IA1, IA2, IB, IC, II and III. Recent methods for discriminating subpopulations within CA phylotypes highlight the predominance of SLST types H1 to 6 or K1 to 20 in bone and joint infection (BJI). The impact of their ability to produce a biofilm during the development of the infection (with resistance / tolerance to antibiotics used for treatment) remains little studied. Method. The purpose of this study was to determine whether the ability to establish a biofilm varied according to the different subtypes of clinical strains of CA previously characterized and involved in BJI (hip, knee and shoulder prosthesis). The BioFilm ring test (BioFilm Control®) method with index determination, called BFI (BioFilm Index) inversely proportional to the level of biofilm production was used (BFI = 0.00 indicates a high production of biofilm versus BFI = 20.00 indicates zero production). The BFI was determined after 3 h (T3) and 6 h (T6) incubation. The strains used came from patients, 5 belonging to the IA1 phylotype (SLST A1 and D1 types) and 4 to different phylotypes (IA2, IB, II and III). Results. The results show that the kinetics of establishment of an early CA biofilm turns out to be phylotype dependent. The most productive strains are those belonging to phylotype II (BFI T3 = 5.73, BFI T6 = 0.00) and to type SLST D1 belonging to phylotype IA1 (BFI T3 = 4.07, BFI T6 = 0.00). The other strains did not demonstrate saturated BFI, even after 6 h of incubation. Conclusions. The exact role of CA, as well as its ability to produce a biofilm in the pathophysiology of BJI, remains poorly understood and the prolonged use of antibiotics to treat these infections is necessary, especially if devices have not been removed, with potential risk of increasing antibiotic resistance and therapeutic failures. CA's different phylotypes demonstrate different biofilm production capabilities, which could have an impact on the antibiotic efficacy suggesting the interest of effective anti-biofilm molecules on metabolically less active strains

Introduction. the aim of the study is to evaluate the clinical results of the shoulder prosthesis revision procedure to reverse implant without removing the humeral stem using a modular system (Lima LTD) and determine if this procedure is beneficial for the patients. Methods. e selected only the patients where a revision to reverse (RSA) of hemiarthroplasty (Hemi) originally implanted for fracture (Group I) and revision to reverse (RSA) of anatomical total prosthesis (TSA) were performed. From 2004 to 2009 26 cases responding to these parameters were identified: 18 cases in Group I (failed hemiarthroplasty for tuberosities resorptions or rotator cuff failure) and 8 in Group II (failed TSA for rotator cuff omplication). The mean follow-up was 32 months (min 18–max 76) and the mean age was 72 (min 65–max 80). Clinical assessment was performed with preoperative and postoperative Constant score rating scale (CS) and range of motion evaluation (ROM). Radiological assessment was performer by AP and Axial X-ray views. Operative time was calculated. Results. overall pre-op CS was 24 (min 18–max 30), post-op CS was 47,8 (min 35–max 60). In Group I the mean improvement of CS was 25,3; in Group II was 17. All patients had a clinical improvement of the range of motion. X-Rays study did not show radiolucent lines related to implant mobilization. No major complications were observed in all the cases. Discussion and Conclusion. Revision surgery for failed Hemi or TSA is commonly related to a relatively increase of complication and/or poorer out come if compared to a primary RSA implant. Our study results demonstrate that using a full modular system from the first implant allows to skip the humeral stem removal/reimplant step in case of conversion of a shoulder prosthesis to a reverse with good clinical result, no radiological signs of mobilization and non major complication probably related to a shorter and less aggressive operative time and procedure

Introduction. The following study start from an idea of the evaluation of the osteointegration in the bone cage of the Equinoxe Reverse shoulder prosthesis. The aim of the study is to assess the values of Bone Mineral Density (BMD) in periprosthetic areas, in patients undergoing shoulder arthroplasty with implants of the Equinoxe system by Excatech, Inc. To better understand the steps of osteointegration time of the bone cage with the glenoid. The objectives of the work are not only expanded to the value of osteointegration, but could also be useful for the evaluation of both mechanical and septic loosening of the stem of the glenoid. Materials and Methods. In the period from November 2011 to May 2012, 15 patients were evaluated. All patients were subjected to bone densitometry type of DXA within the first 15 days after surgery and at 3 months after surgery. The patients are all part of a homogeneous group for anatomical glenoid. Were excluded from the study all patients who were no significant alterations of the head and the glenoid. The acquisitions were performed with the patient in an oblique position, with limb in a neutral position, in order to obtain images in the coronal plane “true” of the joint. Were subsequently calculated values of BMD is around the stem with the 7 areas used by Gruen for the hip prosthesis and peripherally to the central peg using 3 areas, superiorly, medially and inferiorly to the same. Results. The values obtained showed a significant increase in the time of bone density peripherally to the central peg demonstrating a significant osteointegration. Being a prospective study these values will be integrated with new acquisition DXA to 6, 9, 12 months, 2, 3 and 5 years. Conclusions. Although preliminary, through our study it was possible to obtain the standard values of BMD in patients with prosthetic replacement has been successful. These BMD values represent a standard of reference for the physiological osseointegration; in the future must be evaluated for their variation in patients with prosthetic loosening and / or with infectious processes, in order to allow an early diagnosis of these diseases by studying DXA. Also in future studies BMD values obtained by us of the Equinoxe prosthesis can be compared with those obtained in other models of the shoulder prosthesis to detect any advantages or disadvantages in terms of osteointegration

INTRODUCTION. Shoulder joint prostheses have become the most commonly replaced after knee and hip artificial implants. Reverse shoulder arthroplasty (RSA) is the treatment option for patients with severe osteoarthritis, rotator cuff arthropathy or a massive rotator cuff tear with pseudoparalysis. Though successful, the long-term survival of such implants are limited by wear of the materials in contact [1, 2]. The aim of this study was to investigate RSA wear in vitro using a clinically relevant activities of daily living (ADLs). MATERIALS AND METHODS. Four new JRI Orthopaedics Reverse Shoulder 42 mm diameter VAIOS with cobalt-chromium (CoCr) glenospheres and ultra-high molecular weight polyethylene (UHMWPE) humeral components were tested. A five million cycles wear test was undertaken using the unique Newcastle Shoulder Wear Simulator with dilute bovine serum as a lubricant. “Mug to mouth” was performed as the ADL to the test prostheses in intervals of 100 cycles, following by 5 seconds of high load (450N) with no motion simulating an ADL such as “lifting an object”. This combined load cycle was then repeated. A fifth reverse shoulder prosthesis was subject to dynamic loading only in a soak control station. Wear was assessed gravimetrically and roughness (Sa) of the articulating surfaces was measured with a non-contacting profilometer. RESULTS AND DISCUSSION. The mean wear rate and standard deviation of the UHMWPE components was 11.4±3.7 mm. 3. /million cycles, while the CoCr components showed minimal wear over the test duration of 0.01± 0.02 mm. 3. /million cycles (Fig.1). Wear rates are comparable with Kohut et al. (14.1 mm. 3. /million cycles) [3] and Smith et al. (14.3±1.6 mm. 3. /million cycles) [4]. The CoCr glenospheres roughness was unchanged, from 32±8 nm Sa to 28±8 nm Sa over the 5 million cycles of the test (p=0.017), while the UHMWPE humeral components became smoother, from 692±123 nm Sa to 42±29 nm Sa (Fig.2), showing a statically significant change (p<0.001). CONCLUSION. The present study is the first wear test of artificial shoulder joints using a Motion-Load-Motion configuration as a clinically relevant physiological pattern of motion and load. Results are comparable with those found in the literature for in vitro testing of reverse shoulder replacements. For any figures or tables, please contact the authors directly

Background. Scapular notching is a complication after reverse shoulder arthroplasty with a high incidence up to 100%. Its clinical relevance remains uncertain; however, some studies have reported that scapular notching is associated with an inferior clinical outcome. There have been no published articles that studied positional relationship between the scapular neck and polyethylene insert in vivo. The purpose of this study was to measure the distance between the scapular neck and polyethylene insert in shoulders with Grammont type reverse shoulder arthroplasty during active external rotation at the side. Methods. Eighteen shoulders with Grammont type prosthesis (Aequalis Reverse, Tornier) were enrolled in this study. There were 13 males and 5 female, and the mean age at surgery was 74 years (range, 63–91). All shoulders used a glenosphere with 36mm diameter, and retroversion of the humeral implant was 10°in 4 shoulders, 15°in 3 shoulders, and 20°in 11 shoulders. Fluoroscopic images were recorded during active external rotation at the side from maximum internal to external rotation at the mean of 14 months (range, 7–24) after surgery. The patients also underwent CT scans, and three-dimensional glenosphere models with screws and scapula neck models were created from CT images. CT-derived models of the glenosphere and computer-aided design humeral implant models were matched with the silhouette of the implants in the fluoroscopic images using model-image registration techniques (Figure 1). Based on the calculated kinematics of the implants, the closest distance between the scapular neck and polyethylene insert was computed using the scapular model and computer-aided design insert models (Figure 2). The distance was computed at each 5° increment of glenohumeral internal/external rotation, and the data from 20°internal rotation to 40°external rotation were used for analyses. One-way repeated-measures analysis of variance was used to examine the change of the distance during the activity, and the level of significance was set at P < 0.05. Results. The mean glenohumeral abduction during the activity was 17°-22°. The mean distance between the neck and insert was approximately 1mm throughout the activity (Figure 3). The distance tended to become smaller with the arm externally rotated, but the change was not significant. Discussion. The reported incidence of scapular notching after Grammont type reverse shoulder arthroplasty is generally higher than the newer design prosthesis with the lateralized center of rotation. This may be associated with the design of the prosthesis, and the results of this study that the distance between the neck and insert was approximately 1mm throughout active external rotation at the side will support the high incidence of notching. We may need to analyze the distance with the newer design reverse shoulder prosthesis to prove the architectural advantage of the newer systems. Conclusion. The distance between the scapular neck and polyethylene insert was approximately 1mm throughout active external rotation activity in shoulders with Grammont type prosthesis

Introduction:. Given that factors like center of rotation (COR), neck shaft angle, glenosphere diameter and component tilt alter the biomechanics of reverse total shoulder arthroplasty (rTSA), the performance of the total rTSA system is of interest. This study compared the composite performance of two rTSA systems that were designed around a medialized or lateralized glenohumeral COR. The objective was to quantify the following outcome measures: 1) COR & humeral position; 2) range of glenohumeral abduction; 3) force to abduct; and 4) range of internal (IR)/external (ER) rotation. Methods:. Seven pairs of shoulders were tested with a biomechanical shoulder simulator. Beads were implanted in the scapula and humerus to quantify bone positions with a fluoroscope. Spectra lines simulated the deltoid and the rotator cuff. Linear actuators simulated muscle excursion while load cells recorded applied force. Diode arrays were used to quantify arm position and calculate the humeral center of rotation. Native specimens were tested where a motion path was recorded from resting to peak glenohumeral abduction in the scapular plane. The trajectory was replayed and deltoid force vs. arm position was recorded. With the elbow flexed, the arm was articulated to maximal internal and external rotation to determine ROM limits due to impingement or soft tissue constraint. Specimens were implanted with a Tornier Aequalis Reversed Shoulder prosthesis (“A,” 36 mm glenosphere, 10° humeral retroversion, 9 mm poly insert – “medial”) or a DJO Surgical Reverse Shoulder Prosthesis (“R,” 32 mm, 30° retroversion, neutral insert/shell – “lateral”). Implants were randomized between shoulders in a pair. After implantation the test protocol was repeated. Paired-t tests (p ≤ 0.050) were adjusted with Holm's step-down correction for multiple comparisons. Results:. Joint COR shifted inferiorly (A = 7 ± 3 mm, R = 4 ± 2 mm) and medially (A = 19 ± 4 mm, R = 12 ± 3 mm) for both systems with respect to native (p≤0.007, between systems p≤0.037). All humeri shifted inferiorly with respect to native (Fig. 1, p = 0.000, between systems p = 0.718). The RSP maintained a nearly anatomic medial/lateral humerus position, whereas the Aequalis medialized the humerus (p = 0.007). Both rTSA systems showed adduction deficit versus native arms (Fig. 2, p ≤ 0.046). Peak passive abduction, IR and ER were not significantly different between systems (p ≥ 0.113) or with respect to native (p ≥ 0.085). Deltoid force required to elevate the arm decreased ∼25% after rTSA (p ≤ 0.049), but did not differ between systems (p ≥ 0.117). Discussion:. Understanding the implications of implant configuration is imperative to improving implant design and optimizing patient outcomes. As tested, the configurations represent over 70% of respective clinical cases. The systems varied in COR offset, humeral component version/tilt, glenosphere placement, and insert thickness, yet few kinematic differences arose. The RSP COR was more lateral than the Aequalis, yet both were medial to native. Accordingly, both systems provided a similar mechanical advantage by reducing the abduction forces. The RSP had the least adduction deficit, which could indicate increased inferior clearance around the more lateral COR. Inferior and medial humerus shift could negatively impact external rotation capability by moving the posterior cuff line of action below the COR and reducing muscle tension (Fig. 3)